Irradiation method of particle beam therapy system is divided broadly into two methods. That is, a broad irradiation method in which a beam is irradiated into whole of patient's affected area simultaneously and a scanning irradiation method in which a beam is scanned and irradiated. In order to realize a broad beam irradiation method and a scanning irradiation method, equipment and controlling methods which are suited for the irradiation methods are required.
Regarding irradiation apparatuses which are used for conventional scanning irradiation methods, in order to increase accuracy of irradiation position of patient's affected area, a configuration, in which a vacuum region or a region of gas which is lighter than air such as helium is secured and scattering of a beam is suppressed so as to reduce a size of a beam, has been proposed. A part in which a vacuum region or a gas region is secured is indicated as a chamber (beam transport chamber, gas chamber, etc.), or a duct (vacuum duct, etc.). In order to irradiate a beam having a small spot size, an irradiation apparatus which is used for a scanning irradiation method should have a configuration such that a scattering of a beam in a path, before an irradiation object (isocenter) which is caused by air has to be suppressed. Therefore, according to the configuration, right up to an irradiation position is a vacuum region or a gas region, and substances which scatter a beam including an isolation window (beam outlet window) in the region are arranged in the most downstream which is close to an irradiation object.
Further, regarding a broad beam irradiation method, equipment including a spread out Bragg peak forming filter, a collimator and a bolus should be installed in an irradiation apparatus. By using the equipment, an energy distribution of a beam and a beam shape are formed so as to form a particle beam irradiation filed which is suited to a shape of an affected area. According to a broad beam irradiation method, an irradiation field is formed by scattering a particle beam; therefore, it is not necessary to suppress a spot size to be small. Consequently, unlike an irradiation system apparatus which is used for a scanning irradiation method, it is not required to have the configuration such that a vacuum duct is arranged right up to an irradiation object so as to suppress a scattering caused by air in an irradiation apparatus.
As above mentioned, a configuration of a scanning irradiation method and that of a broad beam irradiation are different, therefore, it is difficult to realize a plurality of irradiation methods at one irradiation unit. These irradiation methods have different characteristics and depending on an irradiation part and a shape of an affected part, suited irradiation method is different. As a configuration for realizing a scanning irradiation method and a broad beam irradiation method, Patent Document 1 discloses a configuration, that is, a plurality of treatment rooms are provided, in some of the treatment rooms, an irradiation apparatus of a scanning irradiation method is installed, and in other treatment rooms, an irradiation apparatus of a broad beam irradiation method is installed. However, according to the above-mentioned method, an irradiation unit is required for each irradiation method, therefore, cost as a whole of system is increased. As a configuration for resolving the above-mentioned points, Patent Document 2 discloses a configuration, that is, a gas chamber for suppressing scatter of a particle beam is made to be extendable in the beam traveling direction, and in space which is made by contracting the gas chamber, equipment which is necessary for a broad beam irradiation are inserted so as to enable to realize a broad beam irradiation in the same irradiation unit.